Magnetic separator



March 16, 1937. s, G, FRANTZ MAGNETIC SEPARATOR Filed May 20, 1935 3 Shee cS -Shee't 1 Samuel G.-

March 16, 1937. s, TZ 2,074,085

MAGNET I C SEPARATOR Filed May 20*, 1955 a Sheets shet 2 122081 201' SamuelG. rantz Patented 16, 1937 I UNITED STATES PATENT OFFICE MAGNETIC SEPARATOB Samuel G. Frantz, Princeton, N. J. Application May 2c, 1935, Serial No. 22,283

14 Claims.

The invention relates to improved means for separating particles according to their magnetic susceptibilities.

It is well known that the types of magnetic separators now in general use for dry materials, namely, the pulley, rotor and belt types, are unable to make eilicient separations when fed with fine powders.

One object of my invention is to separate efilciently magnetic material from fine dry mixtures.,

Another object of my invention is to separate magnetic material from mixtures or suspensions of grain in liquids, particularly where the solid 5 particles are extremely small, as for example in the slips and glazes used in the manufacture of china and earthenware. Specifically, one use of my invention is for the separation of iron. from pulverized blast furnace slag.

Other objects will be apparent from this speciflcation. I

In carrying out my invention, I feed a stream, either dry or wet, past a plurality of spaced attractors which are arranged to form a screen.

The attractors are magnetized, preferably from a common source of magneto-motive force. The arrangement of saidattractors as screens and their direction of magnetization is such that in the passage of the stream past said screens, the magnetic particles in said stream are attracted and held thereto.

As illustrative of the principles involved, I describe and show in the accompanying specification and drawings several embodiments of my invention which I have found highly satisfactory under actual conditions of service. In the drawings:--

Fig. i is a vertical cross section through the centre or ems of a device embodying my invention.

Fig. 1a is a horizontal cross section of a part of the same.

Fig. 1b shows a variant of the discharge arrangements of the same device. v

Fig. 2 is a vertical cross section through the axis of a variantof the device shown in Fig. 1.

Figs. 3 and d are respectively a plan and a sectional elevation of another embodiment of my invention, Fig. 4 being taken approximately on the line AA of Fig. 3.

Figs. 5 and 5d are respectively a plan and a sectional elevation" of a variant of the device shown in Fig. 3. I

Fig. 5121s a detail of a part of the device shown inFlg. 5, and

ill

-- space it inside the coil. In order to decrease the reluctance of the magnetic circuit end members 3 and i and shell member 5 may be pro- 10 vided of magnetic material thus economizing electric power, and wire in the winding l. Placed inside the spool are a number of screens 5, which are here shown (and also in Fig. la.) as made up of two strips of magnetic material wound into pan- 15 cake form, each strip having one edge in the top plane and the other edge in the bottom plane of the pancake. One strip is corrugated and the other not, the corrugations serving to space the strips and leave openings between them and form a screen. I have found that very good results are obtained with strips .020 .250 inch, and a depth of corrugation, trough to crest, of about .230 inch.

Whenthe device is to be used to separate mag- 25 netic material from pottery slip and similar liquids in which the solid material remains in sus pension it is preferably provided as shown in Fig. l with a stand pipe I, normally seated at its lower end in t or an extension thereof l3. At 0 about the level of the top screen 6, 'I is perforated with'overfiow'holes 8. A casing g fits inside the screens and around the standpipe leaving a passage lil, annular in cross section between it and l. The upper end of the casing is closed around 35 the standpipe l just above the holes it by a cap ii. A hopper l2 serves to feed the liquid into the device.

In operation, the liquid is fed through it into the'device and flows into the space M, surround- 4O ing the screens. When this space has been filled up to the level of holes 8, the liquid overflows through these holes and is discharged through the bottom of i. It will be seen that the liquid (including suspended material) flows downwardat 45 comparatively low velocity through space M,

which is filled with screens 6, giving ample opliquid emerges from the last screen, rises inside 55 9, overflows into i and is discharged. At the end of a run the device may be cleared of liquid by raising the pipe i to leave an opening around its bottom.

As an alternative to or in addition to the overflow holes in the standpipe, a float la as shown in Fig. 1b may be provided in the hopper l2 arranged to lift the standpipe 1 off its seat when the level of liquid in it rises above a certain point thus allowing the discharge of liquid and solids from the lowest part of the device. This method of discharge is preferred when the solid particles have any tendency to settle out of the liquid and to accumulate in the bottom of the device. When the standpipe is float-operated as in Fig. lb the tube 9 is extended up above the level of liquid in the hopper as shown, to avoid the necessity of a stuffing box and accompanying friction.

The magnetic material retained by the screens may be removed by de-energizing the coil i and flushing out the machine, or by removing the screens 6 and cleaning them.

A device very similar to that shown in Fig. 1 may be used for dry materials. In this case, however, the standpipe i and extension l3 are omitted. Fig. 2 shows an embodiment of my invention so adapted to dry materials. With finely powdered slightly cohesive materials it will usually be necessary to agitate the screens to prevent clogging of the device, and in Fig. 2 I have indicated an agitator or shaker for this purpose in the form of an eccentric weight I5 fixed on a shaft 46 which is rotated by a motor i'i. Clearance is provided between the outside of screens 6 and the inside of 2 to allow a sufllcient motion of the screens.

The devices so far described, and illustrated in Figs. 1 and 2 are very well adaptedto the removal of magnetic material when the latter constitutes but a small fraction, say 1% or less, of the material fed. When larger percentages are present the intervals between cleanings of the screens become inconveniently short, and a modification of the device is to be preferred in which there is continuous automatic removal of magnetic material from the stream and separate discharge thereof.

Figs. 3 and 4 show such embodiment of my invention, Fig. 3 being a view in plan partly cut away, and Fig. 4 being a sectional view in elevation cut along two half diameters at right angles to each other indicated by A-A.

-Coils l1, l2, l3 and similar symmetrically placed coils are placed in two groups as shown in a container l8. They are connected to a source of electric power so that the current in one group flows clockwise and in the other group counter clockwise. If the device is to be used wet the coils must naturally be protected by waterproof coverings. A central post I9 supports one side of each coil, the other side being suitably sup-' ported by the container l8 or otherwise. Top and bottom yoke pieces 3 and l" are preferably of magnetic material, 3'- forming two funnels I2 and 12, and 4 two discharge funnels 20.

Rotatably placed as shown are pancake-shaped screens 6* similar to those already described and having outer flanges 2|. Three vertical shafts 22 are held in bearings as shown and carry flanged wheels 24, whose flanges support the flanges 2| of alternate screens, counting from the top. Another set of three shafts 23, geared to shafts 22 so as to rotate in the opposite direction, carry flanged wheels which support the remaining screens. The three pairs of shafts are connected to a common drive, not shown, and rotated at a moderate speed, so that the screens are rotated at a slow speed, alternate screens moving in opposite series.

In operation material to be separated is fed into the two feed hoppers It and 12. If the device is used wet it should be kept filled with liquid to a level above the top screen at least. The material falls through the vertical space I l enclosed by the coils, encountering there the screens 6 Magnetic particles in the stream are held to the edges of the screen elements and are conveyed by the motion of the screens either clockwise or counter-clockwise out of the space M and out of the magnetic field of the coils into the space 25, in which the magnetic material is dropped into discharge funnel 26.

Another embodiment which is similar in operation to that just described is shown in Figs. 5 and 5a. Fig. 5 is a plan view with the feed hopper removed. Fig. 5a is a sectional elevation through the centre of Fig. 5. In this case the screen 6c is in the form of an endless belt suitably driven as at 2?. Fig. 5b shows a detail of a part of the belt.

A still further variant is shown in Fig. 6. In this figure, the screens 6 are mounted in all or a part of the space between a cone or double-cone member 30 and members 3 and 4 disposed in the stream below the feed hopper. Optionally, the faces, or some of them, of said members 3* 4 and 30 may be corrugated, serrated or otherwise formed as indicated at 31 to provide a multiplicity of concentrations of the magnetic flux.

While the attractor members may be wires of circular cross section magnetized transversely to their axes, I prefer to use, as shown in the drawings and described in this specification, attractor elements whose least dimension measured transverse to the magnetization is small compared to their dimension in the direction of magnetization, that is attractors of elongated cross section. I also prefer an arrangement of attractor elements such that a number of them are in series in the magnetic circuit, and also are in series in the stream. The excellent results which I obtain in practice can be accounted for very largely in theory by these three features.

It is to be understood this specification and the drawings illustrate some preferred forms of my invention, but that my invention is not restricted to those particular forms and devices.

What I therefore claim and desire to secure by Letters Patent is:

1. Magnetic separator comprising a vertical series of horizontally disposed attractor screens, means for magnetizing the same, a standpipe axially of said screens and having an overflow and a discharge, a casing surrounding said standpipe and spaced therefrom but surrounded by said screens, and means for feeding a flow stream through said screens.

2. In a magnetic separator, an attractor screen comprising a thin strip of magnetic material of substantial width compared to thickness, said strip being wound into pancake form and being adapted to be magnetized from edge to edge in the direction of the width of said strip.

3. In a magnetic separator, an attractor screen comprising a pair of strips of magnetic material wound into pancake form, one strip being corrugated and the other plain.

4. In a magnetic separator, an attractor screen comprising a pair of strips of magnetic material wound into pancake form, and means for mag- 9,074,0es v 3 netizing said stnpsfrom edge to edge in the dime tion of width of said strips.

5. A magnetic separator, comprising a magnet coil energizing a magnetic circuit, a casing located in a gap in said circuit and adapted to receive a liquid stream and confine its flow substantially entirely through said gap, said magnetic circuit being closed except for said gap, a plurality of openly spaced elongated magnetizable members arranged transversely of the flux path and distributed throughout the transverse section of the casing and distributed for a'substantial distance in the direction of the flow stream, so that a cross-section taken through said casing normal to the length of any of said members presents in general an array or a multiplicity of discrete cross-sections of such members distributed in two dimensions substantially throughout said casing in said field, the proximity and spacing of said members along the direction of the flux path being respectively sumciently close and so arranged as to form regions oi' lintense and convergent field at their adjacent surfaces in the direction of the flux path. 6. The separator of claim 5, the dimension of said members in the direction of the flux path being greater than their spacing in the same direction.

7. The separator of claim 5, the magnetizable members being-united to form flat foraminous structures with the said members of each structure interattached to provide rigidity of the structure.

8. The separator 01' claim 5 and a magnetizable 5 cone within said casing, the magnetizable members being distributed between the cone and the casing.

,9. A magnetic separator, comprising a magnet coil energizing a magnetic circuit, a casing 10- 40 cated in a gap in said circuit and adapted to receive a flow stream and confine its flow substantially entirely through said gap. said magnetic circuit being closed except for said gap, a plurality of openly spaced magnetiz'able strips of 45 substantial width compared to thickness arranged transversely of the flux path and having their edges disposed normal to the general direction of the flux and their widths disposed sub stantially parallel thereto, distributed throughout the transverse section or the casing and distributed tor a substantial distance in the direction of the flow stream so that a cross-section taken, through said casing normal to the length of any of said strips presents in general an array of a 5 multiplicity of cross-sections of such strips distributed in two dimensions substantially throughout said casing in said field, the proximityof said members along the'direction of the flux path being sufiiciently close to formregions of 10 intense and convergent field at their adjacent surfaces in the direction of the flux path.

10. A magnetic separator comprising a casing, a plurality of magnetizable members disposed in said casing, said members being .thin relatively 15 to their width and narrow relatively to their length, said members lying edgewise and contiguous to one another in staggered relation, and means for magnetizing said members from edge to edge in the direction of their width. 20

11. A magnetic separator comprising a casing,

a plurality of rows of magnetizable members disposed in said casing, said members being thin relatively to their width and narrow relatively to their length, said member lying edgew'ise to one 2; another in staggered relation and contiguous to one another from row to row and means for magnetizing said members from edge to edge in the direction of their width.

12. Attractor unit for a magnetic separator 30 comprising corrugated and substantially flat strips of magnetizable material adapted to be magnetized from edge to edge in the direction of their width and arranged alternately with their sides in contact.

13. The attractor unit of claim 12 in which the alternate corrugated and substantially flat strips are united at their points of contact to form a rigid structure.

14. An attractor unit for a magnetic separator, comprising a plurality of magnetizable strips of thin sheet metal of substantial width compared to thickness, spaced from each other to form grids oi. relatively open mesh, the thickness of said strips being of the same order of magnitude as the size of the largest particles to be caught, said strips being adapted to be magnetized from edge to edge in the direction of their width.-

. SAMUEL G. FRANTZ. 

